The compound 2-mercaptobenzothiazole is a well known and extensively used thiazole accelerator for rubber. It is readily manufactured in high yield and purity by an autoclave reaction of aniline, sulfur and carbon disulfide. Benzothiazole is a by-product in the manufacture of 2-mercaptobenzothiazole and is generally separated from the 2-mercaptobenzothiazole autoclave "melt" by steam distillation.
The use of 2-mercaptobenzothiazole as such and in the form of derivatives, such as sulfenamide accelerators, is growing in direct proportion with the rubber industry. The present processes employed to prepare 2-mercaptobenzothiazole are relatively satisfactory in terms of yield; however, for obvious reasons the complete conversion to 2-mercaptobenzothiazole would be highly desirable. Therefore, the conversion of benzothiazole to 2-mercaptobenzothiazole would present a significant improvement in the art accepted processes for preparing 2-mercaptobenzothiazole.
The present invention represents the culmination of a long series of investigations, conducted largely by the inventors, directed to finding a process for preparing 2-mercaptobenzothiazole from benzothiazole.
Accordingly, it is a primary object of the present invention to find a process for preparing 2-mercaptobenzothiazole from benzothiazole.
It is yet another object of the invention to find a new process for preparing 2-mercaptobenzothiazole using the benzothiazole by-product of the conventional process for preparing 2-mercaptobenzothiazole.
Additional objects and advantages will be set forth in part in the description which follows and in part will be obvious from the description which follows or may be learned by the practice of the invention, the objects and advantages being realized and attained by means of the compositions, processes and improvements, particularly pointed out in the appended claims.